metaxalone (Rx)

Frequency Not Defined

Drug-induced gastrointestinal disturbance

Nausea

Vomiting

Dizziness

Headache

Somnolence

Nervousness

Hemolytic anemia (rare)

Leukopenia (rare)

Jaundice (rare)

Immune hypersensitivity reaction (rare)

Contraindications

Hypersensitivity

History of drug-induced hemolytic anemia

Significant renal/hepatic impairment

Cautions

CNS depression may occur

Sedative effects may be potentiated when used with other sedatives

Medication is poorly tolerated by the elderly

Bioavailability may increase in female patients

Use caution in renal and hepatic impairment

Safety and efficacy not established in children <12 years

May impair physical or mental abilities; caution patient against operating heavy machinery or performing taks requiring mental alertness

Cases of serotonin syndrome, a potentially life-threatening condition, reported during concomitant use of serotonergic drugs with dose within recommended range and with a single agent taken at doses higher than recommended dose; onset of symptoms generally occurs within several hours to a few days, but may occur later than that; discontinue therapy if serotonin syndrome suspected

Sedative effects of and other CNS depressants (eg, alcohol, benzodiazepines, opioids, tricyclic antidepressants (TCAs)) may be additive; exercise caution with patients who take more than one of CNS depressants simultaneously; follow patients closely for signs and symptoms of respiratory depression and sedation

Pregnancy category: C

Lactation: Unknown if excreted in breast milk; not recommended

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

General CNS depression; no direct effect on skeletal muscle; may disrupt the spasm-pain-spasm cycle; does not havae direct effect on skeletal muscle

Absorption

Onset: Within 1 hr

Duration: 4-6 hr

Peak plasma time: 3 hr

Peak plasma concentration: 296 mcg/mL

Distribution

Vd: 800 L

Metabolism

Liver

Metabolites: Unidentified

Elimination

Half-life elimination: 4-14 hr

Excretion: Urine